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Trees and air quality

25 September 2013

LEC researchers are advising government on how the emissions of volatile organic compounds from the terrestrial biosphere should be treated in models of air quality in the UK.

Professor Nick Hewitt and Dr Emily House have been contracted by consultants Ricardo-AEA plc on behalf of the Department of Environment, Food and Rural Affairs (Defra). They are reviewing how these compounds are currently treated in UK air quality models, and advising on how they should be dealt with in future.

Volatile organic compounds, some of which we are familiar with as the characteristic smells of woodlands, meadows and cut grass, play a central role in the chemistry of the lower atmosphere, influencing the formation of ozone and small particles, both of which are important air pollutants.

Modellers of air quality need to include the emissions of these compounds in their calculations, but there are considerable variations in the way this is done, resulting in differences in their predictions of ozone and particles.

In their report Nick and Emily say that more consistency is needed in the way the emission rates of volatile organic compounds are estimated and make suggestions for best practice. This will allow better comparison and understanding of how and why different air quality models give different predictions of the concentrations of ground level ozone. In particular, this will allow the different models of ground level ozone pollution used by Defra contractors to be compared on the basis of their treatment of atmospheric chemical reactions, rather than on their treatment of biogenic emission rates.